Coffee

Coffee is an evergreen shrub or small tree with glossy dark leaves and fragrant white flowers. Its fruit, called a cherry, ripens to red or yellow and usually contains two seeds with flat faces pressed together, known as beans. A single rounder seed in a cherry is called a peaberry.

Green coffee beans are pale and grassy; roasting develops the brown colour and hundreds of aromatic compounds. Arabica is the most prized species for its sweeter, more complex flavour, while robusta, Coffea canephora, is hardier, higher in caffeine and used in instant coffee and espresso blends. Coffee is sold as whole roasted beans, ground, instant and as green beans for home roasting.

Coffea arabica originated in the highland forests of southwestern Ethiopia and neighbouring regions, where wild coffee still grows beneath the forest canopy. Local peoples used the fruit and leaves long before the drink was invented.

Coffee drinking itself is first firmly documented in Yemen in the fifteenth century, among Sufi communities. The English word coffee came via Dutch koffie and Turkish kahve from the Arabic qahwa, which originally was a term for wine or a dark drink. The popular legend of the goatherd Kaldi noticing his goats dancing after eating coffee cherries is a charming story but not a historical record.

From Yemen, coffee spread to Mecca, Cairo and Istanbul in the sixteenth century, where coffeehouses became places of conversation, music and sometimes political suspicion. Yemen's port of Mocha dominated the trade. European travellers brought news of the drink, and by the seventeenth century coffeehouses opened in Venice, London, Paris and Vienna, becoming centres of commerce and debate.

Dutch traders smuggled seedlings out of Arabia and began plantations in Java and Suriname. The French carried coffee to the Caribbean in the 1720s, and Portuguese planters established it in Brazil, which became and remains the world's largest producer. Plantation coffee in the colonial era relied heavily on enslaved labour.

Today coffee is grown in a belt around the equator, in Latin America, Africa, Asia and Oceania, by tens of millions of people, many on small farms. Vietnam is the leading robusta producer. Fair trade and direct-trade models, climate change, leaf rust disease and price volatility are persistent concerns. Coffee culture has evolved through espresso bars, instant coffee, specialty roasters and cold brew.

Coffee beans are roasted, ground and brewed by methods ranging from Turkish ibrik, espresso, moka pot and pour-over to French press and cold brew. Beyond the drink, coffee flavours desserts such as tiramisu, ice cream and mocha, and is used in rubs for meat. Cascara, the dried cherry husk, is brewed as a tea.

Spent grounds are used as garden compost and in skincare scrubs. Traditionally coffee has been used in Ethiopian ceremonies, in Arab hospitality and in folk remedies. Caffeine extracted from coffee or tea goes into soft drinks and medicines.

Large observational studies generally find that moderate coffee drinking, around three to four cups a day, is associated with lower risks of type 2 diabetes, Parkinson's disease and some liver diseases, and is not linked to higher overall mortality. Coffee contains caffeine and antioxidants such as chlorogenic acids, but observational associations cannot prove causation.

Caffeine improves alertness and can disturb sleep, raise heart rate and increase anxiety in sensitive people. Unfiltered coffee, such as French press or boiled coffee, contains compounds that can raise LDL cholesterol. Added sugar and cream often add the most calories.